Photographic triplet objective



Jan. 15, 1952 P. H. TAYLOR PHOTOGRAPHIC TRIPLET OBJECTIVE Filed July 3,1950 q 2 IP62 me: 170? StARCH ROG?" XQO K (4 K i am M5 PITJA/f 417-012.Mar

Patented Jan. 15, 1952 SlLAHU-H KUUM UNITED STATES PATENT OFFICE 2Claims. (01. 8H7) This invention relates to photographic triplets and itis an object of the invention to provide a photographic tripletproducing sharp photographic images over a field of ten degrees andthroughout the spectral region to which panchromatic emulsions aresensitive.

In the present invention three lens components are separated by two airspaces, and a stop is located between the first two elements. with thislens arrangement, spherical aberration, astigmatism, curvature of thefield, the sine condition. coma, and distortion corrections can beattained without producing unduly serious amounts of any aberrations.

In the drawing, the single fi ure illustrates a lens assembly whichcomprises three lens members that are axially aligned and air spaced.Lenses i and 3 are simple collective bi-convex lenses and anintermediate lens I is a dispersive bi-concave lens. A stop is locatedabout 0.70 inch from the pole of the second surface having a radius m.The triplet objective shown has a speed of f/4.9 and an effective focallength of 7 inches. The radii of the three lenses have been indicated as11 and r2, 1-3 and r4, 1's and re. The lenses are separated by airspaces d: and d4 and have axial thickness d1, (la, and (is from front torear, respectively.

Construction data for a 174.9 and 7 inch focal length photographictriplet corrected to produce perfect photographic images over a 10degree field and achromatized for C and F lines of sunlight, built inaccordance with this invention is as follows:

Clear diameter-1.452

Pole oi surface 2 to stop-.7096 Diameter of stop-1.170 9-7.0091

where r is the radius length for an element surface;

d is the axial thickness of an element;

N; is the index of refraction for the F line of hydrogen (4861 D is theindex of refraction for the D line of sodium (5893 L); Y C is the indexof refraction for the C line of hydrogen (6563 L);

BSO-2 is a borosilicate crown glass;

DF-2 is a dense flint glass;

LBC-2 is a light barium crown glass; f is the focal length; and

1' is the back focal length.

The performance of the above prescribed system can be seen from thefollowing aberrations and optical tolerances:

Tolerance =l=.00250 (empirical tolerance) $.00!)

$00250 (empirical tolerance) (extremely sharp definitionf (gooddefinition) *mso (extremely sharp definition) H (extremely sharpdefinition l m .0896 (entirely invisible) (n s izi l where LA is thespherical aberration equal to the back focal length of the paraxial rayminus the back focal length of the marginal ray;

LZA' is the longitudinal zonal aberration;

CS is the offense against the sine condition;

L'ZcL'Zf is the dlflerence in distance of the intersections of the zonalrays on the optical axis of the c and F lines of sunlight;

Zonal or is a third order coefficient which is indicative of lateralcolor error;

Coma'r is coma error in the tangential plane;

Coma, is the coma error in the sasittal plane;

Xr is the distance from a selected focal plane to the focal point of anoff axis object in the tangential plane; (a prime always refers to theX'- is the distance from a selected focal plane 2 to the focal point ofan off axis object for the principal ray in the sagittal plane;

Dist is the measure of distortion;

TChr'nr is the lateral chromatic aberration.

for the D and F lines of sunlight, or any other pair of monochromaticpoints in the spectrum.

The prescription given above can easily be varied to suit variouspurposes as may be desired, by a simple scaling procedure.

When the radii, thicknesses and diameters of the component lenses, forexample, are each multiplied by a constant, and when the efi'ectivefocal length, the back focal length, the linear size of the field, andthe aberrations of the ori inal system are multiplied by the sameconstant, precise values for the new system will be obtained. It is tobe carefully noted that speed (0r f/No.) and angular size of the fieldare not changed. Neither are the optical tolerances changed. It,therefore, follows that if a system of given focal length performssatisfactorily, its

optical behavior can always be improved by constructing a smaller scalemodel. Should a larger scale model be desired, consideration must begiven to the ratio each aberration bears to its tolerance in theoriginal prescription, since this ratio is subject to multiplication bythe i scaling constant.

What is claimed is:

1. An objective lens .of the character described comprising threeaxially aligned and airspaced lens members, the first and third membersbeing simple collective bil-conyex lenses, the second member being adispersive bi-concave lens, and an aperture stop in the air spacebetween said first and third members, said' system" 'having thefollowing "prescription:

Prescription Glau BBC-2 1. 52264 1. 51462 LBC-Z 1. 57950 1. 56960 wherer is the radius length for an element surface;

d is the axial thickness of an element;

Np is the index of refraction for the F line of hydro gen (4861 A.

N is theA index of refraction for the D line of sodium N is the index ofrefraction for the C line of hydrogen (6563 1. i

v N 3- NC,

BSC-2 is a borosilicate crown glass;

DF-2 is a dense flint glass;

LBC-2 is a light barium crown glass;

f is the focal length; and

1' is the back focal length.

each multiplied by a constant K differing from zero:

Prescription Glass N N BBC-2 1. 62264 1. 51462 LEG-2 1. 57950 1.57250 1. 56960 PHILIP H. TAYLOR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,892,162 Richter Dec. 27, 19321,987,878 Tronnier Jan. 15, 1935 2,298,090 Warmisham Oct. 6, 19422,388,869 Reiss Nov. 13, 1945 2,430,550 Altman et al. Nov. 11, 19472,487,873 Herzberger et al. Nov. 15, 1949

